U.S. patent application number 16/812594 was filed with the patent office on 2020-09-24 for spark plug and method of producing the same.
The applicant listed for this patent is DENSO CORPORATION. Invention is credited to Masataka DEGUCHI.
Application Number | 20200303905 16/812594 |
Document ID | / |
Family ID | 1000004698747 |
Filed Date | 2020-09-24 |
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United States Patent
Application |
20200303905 |
Kind Code |
A1 |
DEGUCHI; Masataka |
September 24, 2020 |
SPARK PLUG AND METHOD OF PRODUCING THE SAME
Abstract
A spark plug has a housing of a cylindrical shape, an insulator
of a cylindrical shape, and a packing. The housing has a housing
facing surface. The insulator has an insulator facing surface and
is supported in the housing. The packing has an insulator side
contact surface which is in contact with the insulator facing
surface. The packing is arranged between the housing facing surface
and the insulator facing surface to face both the housing facing
surface and the insulator facing surface. The packing has proximal
inner circumferential surfaces formed adjacent with the inner
periphery side of the insulator side contact surface. Each of the
proximal inner circumferential surfaces has a curved shape smoothly
connected to the insulator side contact surface of the packing.
Inventors: |
DEGUCHI; Masataka;
(Kariya-city, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DENSO CORPORATION |
Kariya-city |
|
JP |
|
|
Family ID: |
1000004698747 |
Appl. No.: |
16/812594 |
Filed: |
March 9, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01T 13/36 20130101;
H01T 21/02 20130101 |
International
Class: |
H01T 13/36 20060101
H01T013/36; H01T 21/02 20060101 H01T021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 21, 2019 |
JP |
2019-053957 |
Claims
1. A spark plug comprising: a housing of a cylindrical shape
comprising a housing facing surface; an insulator of a cylindrical
shape comprising an insulator facing surface, the insulator being
supported in the housing; and a packing comprising an insulator
side contact surface formed in contact with the insulator facing
surface of the insulator, wherein the packing is arranged between
the housing facing surface of the housing and the insulator facing
surface of the insulator so as to face both the housing facing
surface and the insulator facing surface, and the packing comprises
proximal inner circumferential surfaces, formed adjacent with the
inner periphery side of the insulator side contact surface, having
a curved shape which is smoothly connected to the insulator side
contact surface of the packing.
2. The spark plug according to claim 1, wherein on a cross section
of the packing in a direction parallel with a pug axial direction
of the spark plug passing through a central axis of the packing,
each of the proximal inner circumferential surfaces of the packing
has a curvature radius of not less than 5 .mu.m.
3. The spark plug according to claim 1, wherein the packing further
comprises a housing side contact surface arranged in contact with
the housing facing surface of the housing, and burr lines are
formed at inner periphery side edges of the housing side contact
surface of the packing along a plug circumferential direction.
4. The spark plug according to claim 2, wherein the packing further
comprises a housing side contact surface arranged in contact with
the housing facing surface of the housing, and burr lines are
formed at inner periphery side edges of the housing side contact
surface of the packing along a plug circumferential direction.
5. The spark plug according to claim 1, wherein the packing further
comprises proximal outer circumferential surfaces formed adjacently
at outer periphery side of the insulator side contact surface, and
each of the proximal outer circumferential surfaces has a curved
shape which is smoothly connected to the insulator side contact
surface of the packing.
6. The spark plug according to claim 2, wherein the packing further
comprises proximal outer circumferential surfaces formed adjacently
at outer periphery side of the insulator side contact surface, and
each of the proximal outer circumferential surfaces has a curved
shape which is smoothly connected to the insulator side contact
surface of the packing.
7. The spark plug according to claim 3, wherein the packing further
comprises proximal outer circumferential surfaces formed adjacently
at outer periphery side of the insulator side contact surface, and
each of the proximal outer circumferential surfaces has a curved
shape which is smoothly connected to the insulator side contact
surface of the packing.
8. The spark plug according to claim 5, wherein each of distal
inner circumferential surfaces formed adjacent to the inner
periphery side of the housing side contact surface and distal outer
circumferential surfaces formed adjacent to the outer periphery
side of the housing side contact surface has a curved surface which
is smoothly connected to the housing side contact surface.
9. The spark plug according to claim 6, wherein each of distal
inner circumferential surfaces formed adjacent to the inner
periphery side of the housing side contact surface and distal outer
circumferential surfaces formed adjacent to the outer periphery
side of the housing side contact surface has a curved surface which
is smoothly connected to the housing side contact surface.
10. The spark plug according to claim 7, wherein each of distal
inner circumferential surfaces formed adjacent to the inner
periphery side of the housing side contact surface and distal outer
circumferential surfaces formed adjacent to the outer periphery
side of the housing side contact surface has a curved surface which
is smoothly connected to the housing side contact surface.
11. A method of producing the spark plug according to claim 1,
comprising steps of: punching a plate member to produce a packing;
and arranging the packing between a housing facing surface of a
housing and an insulator facing surface of an insulator so as to
face both the housing facing surface and the insulator facing
surface, and press burrs formed by the step of punching the plate
member are arranged at the housing facing surface side, and press
sagging formed by the step of punching the plate member are
arranged at the insulator facing surface side; and pressing the
insulator in the housing through the packing in a distal end
direction of the spark plug.
12. The method according to claim 11, wherein the step of punching
the plate member to produce the packing uses a first forming die
having a cylindrical shape, a punching tool to be inserted inside
the first forming die, and a second forming die having a
cylindrical shape to be arranged facing the first forming die in a
formation direction of the first forming die, a first facing
surface of the first forming die has a tapered shape formed
inwardly along a first direction of the formation direction, and a
second facing surface of the second forming die has a tapered shape
formed inwardly along a second direction of the formation
direction, the first direction is in opposite to the second
direction, the first facing surface of the first forming die and
the second facing surface of the second forming die are arranged
facing from each other in the formation direction of the first
forming die, the step of punching the plate member comprises a
first punching step and a second punching step, wherein in the
first punching step, the punching tool punches a part at an inner
periphery side of the plate member in the second direction from the
first direction of the first forming die so as to produce a packing
member, and in the second punching step, the packing member is
arranged between the first facing surface of the first forming die
and the second facing surface of the second forming die, and the
second forming die pushes the packing member in the first forming
die to produce the packing having a tapered shape which is tapered
inwardly in the first direction of the second facing surface of the
second forming die.
13. A method of producing the spark plug according to claim 5,
comprising steps of: punching a plate member to produce a packing
member having a ring shape; and performing a barrel polishing so as
to polish the packing member having proximal inner circumferential
surfaces of a curved shape, proximal outer circumferential surfaces
of a curved shape, distal inner circumferential surfaces of a
curved shape, and distal outer circumferential surfaces of a curved
shape.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is related to and claims priority from
Japanese Patent Application No. 2019-53957 filed on Mar. 21, 2019,
the contents of which are hereby incorporated by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to spark plugs and methods of
producing a spark plug.
BACKGROUND
[0003] A known spark plug has a housing and an insulator. The
housing is made of low carbon steel and has a cylindrical shape.
The insulator is made of alumina and has a cylindrical shape. The
insulator is arranged inside the housing. The housing has a
stepwise structure in which a stepwise shape is formed on an inner
periphery side of the housing to be projected from an inner
circumferential wall. The insulator is supported by a proximal end
side surface of the stepwise shape through a packing member. The
packing member is made of metal and has a ring shape. The packing
member allows a chamber between the housing and the insulator to
maintain its air tightness.
[0004] The spark plug previously described has pointed corners
formed on the inner periphery side and an outer periphery side of
the surface which are in contact with the insulator at the packing
member side. This structure may cause generation of cracks in the
insulator due to a large force applied from the pointed corners to
the insulator side. In particular, cracks are generated in the
insulator from the outer circumferential surface of the insulator
to the diameter direction of the spark plug due to the magnitude of
force applied from the pointed corners at the inner periphery side
of the packing to the insulator. This often causes the insulator to
be broken.
SUMMARY
[0005] It is desired for the present disclosure to provide a spark
plug having a housing, an insulator and a packing. The housing has
a cylindrical shape. The housing has a housing facing surface. The
insulator has a cylindrical shape. The insulator has an insulator
facing surface. The insulator is supported in the housing. The
packing has an insulator side contact surface formed in contact
with the insulator facing surface of the insulator. The packing is
arranged between the housing facing surface of the housing and the
insulator facing surface of the insulator so as to face both the
housing facing surface and the insulator facing surface. The
packing has proximal inner circumferential surfaces formed adjacent
with the inner periphery side of the insulator side contact
surface. Each of the proximal inner circumferential surfaces has a
curved shape which is smoothly connected to the insulator side
contact surface of the packing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] A preferred, non-limiting embodiment of the present
disclosure will be described by way of example with reference to
the accompanying drawings, in which:
[0007] FIG. 1 is a view showing a half cross section of a spark
plug according to a first exemplary embodiment of the present
disclosure;
[0008] FIG. 2 is an enlarged view of a surrounding part of a
packing in the spark plug shown in FIG. 1;
[0009] FIG. 3 is a perspective view of the packing in the spark
plug according to the first exemplary embodiment shown in FIG.
1;
[0010] FIG. 4 is a schematic view showing a housing side contact
surface at a housing side of the packing shown in FIG. 3;
[0011] FIG. 5 is a view showing a method of producing a packing
according to the first exemplary embodiment, in particular, showing
a schematic cross section of a structure in which a plate member is
arranged on a die to produce the packing;
[0012] FIG. 6 is a view showing the method of producing the packing
according to the first exemplary embodiment, in particular, showing
a schematic cross section of the packing produced by punching the
plate member;
[0013] FIG. 7 is a view showing a cross section of the packing
produced by the method shown in FIG. 6;
[0014] FIG. 8 is a view showing a method of producing the spark
plug according to the first exemplary embodiment, in particular,
showing a partially enlarged cross section of a structure in which
the packing is assembled with the housing in the spark plug
according to the first exemplary embodiment;
[0015] FIG. 9 is a view showing the method of producing the spark
plug according to the first exemplary embodiment, in particular,
showing a partially enlarged cross section of a structure in which
the insulator is inserted into the housing in the spark plug
according to the first exemplary embodiment;
[0016] FIG. 10 is a view showing the method of producing the spark
plug according to the first exemplary embodiment, in particular,
showing a partially enlarged cross section of a structure in which
the packing is arranged in and fitted to the gap between the
housing and the insulator in the spark plug;
[0017] FIG. 11 is an enlarged view of the surrounding part of the
packing in the spark plug produced by the method according to a
second exemplary embodiment of the present disclosure;
[0018] FIG. 12 is a view showing the method of producing the
packing according to the second exemplary embodiment, in
particular, showing a schematic view of a packing member and a
method of polishing the packing member to form the packing in the
spark plug;
[0019] FIG. 13 is a view showing the method of producing the
packing in the spark plug according to a third exemplary
embodiment, in particular, showing the packing member and a surface
pressing jig before pressing the packing member by using the
surface pressing jig;
[0020] FIG. 14 is a view showing the method of producing the
packing according to the third exemplary embodiment, in particular,
showing the packing member with burr lines formed by pressing the
press burrs shown in FIG. 13 on the surface of the packing
member;
[0021] FIG. 15 is a view showing a packing formation step composed
of a first formation step and a second formation step according to
a fourth exemplary embodiment of the present disclosure;
[0022] FIG. 16 is a view showing the second formation step in the
packing formation step according to the fourth exemplary
embodiment, in particular, showing a cross section of the packing
in the second formation step after the first formation step;
[0023] FIG. 17 is a view showing the packing produced by the
packing formation step according to the fourth exemplary embodiment
of the present disclosure;
[0024] FIG. 18 is a view showing the method of assembling the
packing with the housing and the insulator in the spark plug
according to the fourth exemplary embodiment, in particular,
showing a partially enlarged cross section of a structure in which
the packing is arranged between the housing and the insulator in
the spark plug according to the first exemplary embodiment; and
[0025] FIG. 19 is a view showing the method of producing the spark
plug according to the fourth exemplary embodiment, in particular,
showing a partially enlarged cross section of the spark plug in
which the packing is deformed between the housing and the insulator
by an assemble step according to the fourth exemplary
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Hereinafter, various embodiments of the present disclosure
will be described with reference to the accompanying drawings. In
the following description of the various embodiments, like
reference characters or numerals designate like or equivalent
component parts throughout the several diagrams.
First Exemplary Embodiment
[0027] A description will be given of a spark plug according to a
first exemplary embodiment of the present disclosure and of a
method of producing the spark plug according to the first exemplary
embodiment with reference to FIG. 1 to FIG. 10.
[0028] FIG. 1 is a view showing a half cross section of the spark
plug 1 according to the first exemplary embodiment of the present
disclosure. FIG. 2 is an enlarged view of a surrounding part of a
packing 4 in the spark plug 1 shown in FIG. 1.
[0029] As shown in FIG. 1 and FIG. 2, the spark plug 1 according to
the first exemplary embodiment has a housing 2 and an insulator
3.
[0030] As shown in FIG. 1, the housing 2 has a cylindrical shape.
The insulator 3 is arranged inside the housing 2. As shown in FIG.
2, the packing 4 is supported by a housing facing surface 21 of the
housing 2 and an insulator facing surface 31 of the insulator 3,
where the housing facing surface 21 of the housing 2 is arranged
facing the insulator facing surface 31 of the insulator 3.
[0031] The packing 4 has an insulator side contact surface 41 which
is formed in contact with the insulator facing surface 31 of the
insulator 3. The packing 4 has proximal inner circumferential
surfaces 431 formed adjacently at the inner periphery side of the
insulator side contact surface 41 of the packing 4. Each proximal
inner circumferential surface 431 has a curved surface which is
smoothly fitted to the insulator side contact surface 41 of the
packing 4.
[0032] A description will now be given of a detailed structure of
the spark plug 1 according to the first exemplary embodiment.
[0033] The spark plug 1 according to the first exemplary embodiment
is applied to internal combustion engines mounted on motor
vehicles, and co-generation systems. The spark plug 1 according to
the first exemplary embodiment is used as an ignition device to
ignite a combustion in an internal combustion engine. One side of
the spark plug 1 according to the first exemplary embodiment is
connected to an ignition coil (not shown) in a plug axial direction
Z. The other side of the spark plug 1 is arranged in the combustion
chamber of the internal combustion engine.
[0034] A central axis of the spark plug 1 will be referred to as
the plug central axis. A proximal end side of the spark plug 1 is
connected to the ignition coil (not shown), and a distal end side
(or a front end side) of the spark plug 1 is arranged inside the
combustion chamber of the internal combustion engine. A
circumferential direction of the spark plug 1 will be referred to
as the plug circumferential direction. A radial direction of the
spark plug 1 will be referred to as the plug radial direction.
[0035] The housing 2 has a cylindrical shape and is made of heat
resistance metal material such as iron, nickel, iron nickel alloy,
stainless steel, etc. As shown in FIG. 1, the housing 2 supports
the insulator 2 arranged in an inside chamber at the inner
periphery side of the housing 2.
[0036] An attachment screw part 22 is formed at the distal end side
of the housing 2. The attachment screw part 22 of the housing 2 is
screwed into a female screw hole formed in a plug hole of an engine
head of the internal combustion engine. This allows the spark plug
1 to be mounted on the internal combustion engine. That is, the
spark plug 1 is mounted on the engine head of the internal
combustion engine when the attachment screw part 22 is engaged with
the female screw part of the plug hole. The distal end side of the
spark plug 1 is arranged inside the combustion chamber of the
internal combustion engine.
[0037] As shown in FIG. 1 and FIG. 2, the housing has a projection
part 210 which is projected from a part of the inner
circumferential surface of the housing in the inner periphery
side.
[0038] The projection part 210 is formed at the distal end side of
the housing 2. That is, the projection part 210 is formed at the
inner periphery side of the attachment screw part 22. The
projection part 210 has a ring shape formed on the overall inner
circumferential surface of the housing 2. As shown in FIG. 1, the
projection part 210 has the minimum inner diameter of the housing
2.
[0039] As shown in FIG. 2, the proximal end side surface of the
projection part 210 corresponds to the housing facing surface 21
which will be explained later.
[0040] The housing facing surface has a taper shape which is
tapered in the inner periphery side along the distal end side of
the housing 2 in the spark plug axial direction Z. As shown in FIG.
2, the insulator 2 is supported by the housing facing surface 21 of
the housing 2 through the packing 2.
[0041] The insulator 3 has a cylindrical shape made of insulation
member such as alumina. As shown in FIG. 1, the insulator 3 is
supported by the housing 2 so that the distal end side and the
proximal end side of the insulator 3 are projected from the housing
2 viewed along the plug axial direction Z.
[0042] An insulator leg part 32 is formed at the distal end side of
the insulator 3 so that an outer diameter of the insulator leg part
32 is reduced in the distal end side of the insulator 2.
[0043] The distal end side part of the insulator leg part 32 is
projected from the distal end side of the housing 2. An insulator
stepwise part 310 is formed so that the insulator leg part 32 is
arranged adjacent to a proximal end part of the insulator leg part
32.
[0044] The insulator stepwise part 310 has a diameter which
increases in the proximal end side of the spark plug 1 in the plug
axial direction Z. The outer circumferential surface of the
insulator stepwise part 310 forms the insulator facing surface 31
of the insulator 3.
[0045] The insulator facing surface 31 has a taper shape which is
tapered outwardly from the insulator leg part 32 in the proximal
end side of the insulator 3. The insulator facing surface 31 of the
insulator 3 is arranged facing the housing facing surface 21
substantially parallel from each other.
[0046] As shown in FIG. 2, the inner circumferential edge part of
the insulator facing surface 31 is arranged slightly and inwardly
projecting from the projection part 210 formed at the distal end
side of the housing 2.
[0047] The insulator leg part 32 is formed from the inner
circumferential edge part to the distal end side of the insulator
3. This arrangement provides a gap c between the projection part
210 of the housing 2 and the insulator leg part 32 in a plug radial
direction which is perpendicular to the plug axial direction Z (see
FIG. 2).
[0048] The packing 4 is fitted to the gap between the insulator
facing surface 31 of the insulator 3 and the housing facing surface
21 of the housing 2. That is, the packing 4 is supported by the
housing 2 and the insulator 3.
[0049] FIG. 3 is a perspective view of the packing 4 in the spark
plug 1 according to the first exemplary embodiment shown in FIG. 1.
As shown in FIG. 3, the packing 4 is produced by forming metal
material in a ring shape. For example, it is possible to punch a
cold reduced carbon steel sheet (SPCD of the Japanese Industrial
Standard). A detailed method of producing the packing 4 will be
explained later.
[0050] As shown in FIG. 2, the packing 4 is formed to be fitted in
a gap formed between the insulator facing surface 31 and the
housing facing surface 21 which face from each other in the normal
direction of the insulator facing surface 31 and the insulator leg
part 32.
[0051] The packing 4 is not arranged at an inner periphery side of
the insulator facing surface 31. In addition, the packing 4 is not
arranged in the gap c formed between the projection part 210 of the
housing 2 and the insulator 3. Further, the packing 4 is not in
contact with the side surface of the insulator leg part 32 of the
insulator 3.
[0052] When the packing 4 is arranged in the gap c shown in FIG. 2,
the packing 4 presses the insulator 3 in the radial direction of
the spark plug 1. This arrangement reduces a strength of the
insulator 3 in the spark plug 1. Accordingly, it is preferable to
avoid the packing 4 from being arranged in the gap c.
[0053] The packing 4 has a taper shape which is tapered in the
distal end side thereof in the inner periphery side so as to fit
the insulator facing surface 31 and the housing facing surface
21.
[0054] The packing 4 has the insulator side contact surface 41, a
housing side contact surface 42, an inner periphery side surface 43
and an outer periphery side surface 44.
[0055] As previously described, the insulator side contact surface
41 is arranged in contact with the insulator facing surface 31 of
the insulator 3. As shown in FIG. 2, the housing side contact
surface 42 is arranged in contact with the housing facing surface
21 of the housing 2. The inner circumferential end of the insulator
side contact surface 41 is connected to the inner circumferential
end of the housing side contact surface 42 through the inner
periphery side surface 43. The outer circumferential end of the
insulator side contact surface 41 is connected to the outer
circumferential end of the housing side contact surface 42 through
the outer periphery side surface 44.
[0056] As previously described, the proximal inner circumferential
surface 431 is formed adjacent to the inner periphery side of the
insulator side contact surface 41 of the packing. The proximal
inner circumferential surface 431 has a curved surface capable of
being smoothly fitted to the insulator side contact surface 41 of
the packing 4.
[0057] The proximal inner circumferential surface 431 is formed on
the end part of the insulator side contact surface 41 at the inner
periphery side surface 43 side. As shown in FIG. 2, the proximal
inner circumferential surface 431 has a curved surface of a chamfer
at the proximal end side of the packing 4 in a diagonally inner
circumferential direction. The proximal inner circumferential
surface 431 is formed on the packing 4 along the overall plug
circumferential direction. On a cross section of the packing 4
along the central axis of the spark plug 1 and is parallel to the
plug axial direction Z, the proximal inner circumferential surface
431 has a curvature radius of not less than 5 .mu.m.
[0058] The packing 4 further has a proximal outer circumferential
surface 441 formed adjacently at the outer periphery side of the
insulator side contact surface 41. The proximal outer
circumferential surface 441 has a curved surface which is smoothly
connected to the insulator side contact surface 41.
[0059] The proximal outer circumferential surface 441 in the outer
periphery side surface 44 is formed at the end part of the
insulator side contact surface 41. The proximal outer
circumferential surface 441 has a curved surface of a chamfer at
the proximal end side of the packing 4 in a diagonally outer
circumferential direction.
[0060] The proximal outer circumferential surface 441 is formed on
the packing 4 along the overall plug circumferential direction. On
a cross section of the packing 4 along the central axis of the
spark plug 1 and is parallel to the plug axial direction Z, the
proximal outer circumferential surface 441 has a curvature radius
of not less than 5 .mu.m.
[0061] FIG. 4 is a schematic view showing the housing side contact
surface 42 at the housing side of the packing 4 shown in FIG. 3. As
shown in FIG. 4, a burr line 45 is formed at the inner
circumferential edge part and the outer circumferential edge part
of the housing side contact surface 42 of the packing 4 along the
plug circumferential direction.
[0062] The burr line 45 has been formed on the packing 4 before the
packing 4 is assembled with the spark plug 1. Press burrs 401 shown
in FIG. 7 projecting in the distal end side of the packing 4 are
deformed and crushed by the housing facing surface 21 when the
packing 4 is assembled with the spark plug 1.
[0063] When viewed from the distal end side, the burr line 45 in
the packing 4 assembled with the spark plug 1 has a circular shape
along the overall circumferential in the plug circumferential
direction. The formation of the burr line 45 in the packing 4 will
be explained later.
[0064] It is accordingly possible to detect the burr line 45 formed
in the packing 4 based on the presence of the burr line 45 of the
packing 4 assembled with the spark plug 1.
[0065] It is possible to recognize that the packing 4 has been
produced from a plate member 400 by the punching step which has
punched the other parts in the plate member 400, excepting for the
part forming the packing 4, in the direction to which the press
burrs project.
[0066] As shown in FIG. 1, a central electrode 11, a glass seal 12,
a resistance 13 and a terminal fitting 14 are arranged inside the
insulator 3. The central electrode 11 has a cylindrical shape made
of nickel base alloy. In particular, a metal material having a
superior thermal conductivity such as Cu, etc. is arranged in the
central electrode 11. The central electrode 11 is arranged
projecting from the insulator 3 in the distal end side of the spark
plug 1. The resistance 13 is arranged at the proximal end side of
the central electrode 11 through the glass seal 12 in the insulator
3.
[0067] The resistor 13 is produced by heating and sealing a
resistance composite of glass power and a resistance material such
as carbon or ceramics powder. It is acceptable to insert a
cartridge type resistor as the resistor 13 into the insulator
3.
[0068] The glass seal 12 is made of copper glass produced by mixing
copper powder into a glass member. The terminal fitting 14 is
arranged at the proximal end side of the resistor 13 in the
insulator 3 through the glass seal 12 made of copper glass. For
example, the terminal fitting 14 is made of iron alloy. The spark
plug 1 is electrically connected to the ignition coil (not shown)
through the terminal fitting 14.
[0069] A ground electrode 15 is connected to a distal end surface
(or a front end surface) of the housing 2. A discharge gap G is
formed between the central electrode 11 and the ground electrode
15. A part of the ground electrode 15 is arranged facing the distal
end surface of the central electrode 11 in the plug axial direction
Z. That is, the discharge gap G is formed between the distal end
surface of the central electrode 11 and the ground electrode 15 in
the plug axial direction Z. A spark discharge is created in the
discharge gap G of the spark plug 1 so as to ignite a fuel mixture
in the combustion chamber of the internal combustion engine.
[0070] A description will be given of the method of producing the
spark plug 1 according to the first exemplary embodiment with
reference to FIG. 5 to FIG. 9.
[0071] First, a description will now be given of the method of
producing the packing 4 with reference to FIG. 5 to FIG. 7.
[0072] FIG. 5 is a view showing the method of producing the packing
4 in the spark plug 1 according to the first exemplary embodiment.
In particular, FIG. 5 shows a schematic cross section of a
structure in which the plate member 400 is arranged on a die 51 to
produce the packing 4. As shown in FIG. 5, a punching step punches
a plate member 400 so as to produce the packing 4. In more detail,
the punching step uses a punching tool 50 and a cylindrical die 51
shown in FIG. 5. In the punching step shown in FIG. 5, the plate
member 400 is arranged on a mounting surface 511 at the end of the
cylindrical die 51. The mounting surface 511 of the die 51 has a
circular plate shape.
[0073] FIG. 6 is a view showing the method of producing the packing
4 according to the first exemplary embodiment, in particular,
showing a schematic cross section of the packing 4 produced by
punching the plate member 400.
[0074] As shown in FIG. 5 and FIG. 6, the punching tool 50 punches
the plate member 400 from the opposite surface of the die 51. The
punching tool 50 punches the parts at the inner periphery side of
the plate member 400 and the outer circumferential part of the
plate member 400 viewed from the die 51. As previously described,
the punching step produces the packing 4 having a ring shape.
[0075] FIG. 7 is a view showing a cross section of the packing 4
produced by the method shown in FIG. 6. As shown in FIG. 7, press
burrs 401 are formed at the inner circumferential edge and the
outer circumferential edge around the overall circumferential of
the packing 400 after the punching tool 50 punches the plate member
400. Further, as shown in FIG. 7, a press sagging 402 of a curved
shape are also generated at the corners of the packing 4 opposite
to the projection side of the press burrs 401 around the overall
circumferential of the packing 4.
[0076] A description will be given of the method of assembling the
packing 4 with the spark plug 1 with reference to FIG. 8 to FIG.
10.
[0077] FIG. 8 is a view showing the method of producing the spark
plug 1 according to the first exemplary embodiment. In particular,
FIG. 8 showing a partially enlarged cross section of a structure in
which the packing 4 is assembled with the housing 2 in the spark
plug 1.
[0078] As shown in FIG. 8, the packing 4, which has been produced
by the method previously described, is arranged on the housing
facing surface 21 of the housing 2 so that the press burrs 401 are
formed at the housing facing surface 21 side, and the press sagging
402 is formed at the opposite (i.e. in the proximal end side) of
the housing facing surface 21.
[0079] FIG. 9 is a view showing the method of producing the spark
plug 1 according to the first exemplary embodiment. In particular,
FIG. 9 shows a partially enlarged cross section of a structure in
which the insulator 3 is inserted into the housing 2 in the spark
plug 1 according to the first exemplary embodiment. FIG. 10 is a
view showing the method of producing the spark plug 1 according to
the first exemplary embodiment. In particular, FIG. 10 shows a
partially enlarged cross section of a structure in which the
packing 4 is arranged in and fitted to the gap between the housing
2 and the insulator 3 in the spark plug 1.
[0080] As shown in FIG. 9, the insulator 3 is inserted inside the
housing 2 from the proximal end side of the housing 2 until the
insulator facing surface 31 of the insulator 3 becomes in contact
with the packing 4. After this, the insulator 3 is pressed to the
housing 2 side in the distal end direction of the spark plug 1.
This pressing deforms the shape of the packing 4, and the shape of
the packing 4 tapers inwardly in the distal end side of the housing
2 along the insulator facing surface 31 of the insulator 3 and the
housing facing surface 21 of the housing 2.
[0081] The insulator side contact surface 41 at the proximal end
side of the packing 4 is in contact with the insulator facing
surface 31 of the housing 3. The press sagging 402 adjacent to the
inner periphery side of the insulator side contact surface 41 forms
the proximal inner circumferential surface 431. The press sagging
402 adjacent to the outer periphery side of the insulator side
contact surface 41 forms the proximal outer circumferential surface
441.
[0082] The press burr 401 formed at the distal end side of the
packing 4 is pressed by the housing facing surface 21 of the
housing 2. As shown in FIG. 4, the burr line 45 is formed around
the inner circumferential edge and the outer circumferential edge
of the housing side contact surface 42 of the packing 4.
[0083] As previously described, the packing 4 is assembled with the
spark plug 1 and fitted between the housing 2 and the insulator
3.
[0084] A description will be given of behavior and effects of the
spark plug 1 with the packing 4 and the method according to the
first exemplary embodiment.
[0085] In the structure of the spark plug 1 according to the first
exemplary embodiment, the proximal inner circumferential surface
431, formed adjacent to the inner periphery side of the insulator
side contact surface 41 in the packing 4, has the curved surface
which is smoothly connected to the insulator side contact surface
41. This structure makes it possible to reduce the magnitude of
force applied to the insulator 3 to the insulator 3 from the inner
periphery side of the insulator side contact surface 41 of the
packing 4 through the insulator facing surface 31. Accordingly,
this structure of the spark plug 1 makes it possible to suppress
the insulator 3 from being broken due to progress of cracks from
the insulator facing surface 31 in the central point of the spark
plug 1 in the plug radial direction, i.e. in the radial direction
of the spark plug 1.
[0086] On a cross section of the packing 4 which is in parallel
with the plug axial direction Z which is on the central axis of the
spark plug 1, each proximal inner circumferential surface 431 of
the packing 4 has a curvature radius of not less than 5 .mu.m. This
structure makes it possible to smoothly connect the insulator side
contact surface 41 to the proximal inner circumferential surface
431 in the packing 4. This structure more reduces the force applied
from the packing 4 to the insulator 3. The experimental results
regarding the force applied from the packing 4 to the insulator 3
will be explained later.
[0087] The burr line 45 is formed on the housing side contact
surface 42 of the packing 4 along the inner circumferential edge
part of the housing side contact surface 42. That is, the packing 4
is produced by the punching step previously described. Each
proximal inner circumferential surface 431 having a curved surface
is produced by using the press sag 402 formed at the location
opposite to the press burr 401 (see FIG. 7). This makes it possible
to easily produce the packing 4.
[0088] In addition to the proximal inner circumferential surfaces
431 of the packing 4, the proximal outer circumferential surface
441 also has a curved surface which is smoothly connected to the
insulator side contact surface 41. This makes it possible to
further reduce the magnitude of force applied from the packing 4 to
the insulator 3.
[0089] In the method of producing the spark plug 1, the punching
tool 50 punches the plate member 400 to produce the packing 4.
[0090] The packing 4 is arranged between the housing facing surface
21 of the housing 2 and the insulator facing surface 31 of the
insulator 3 so that the press burr 401 of the packing 4 is formed
at the housing facing surface 21 side and the press sagging 402 is
formed at the insulator facing surface 31 side. This arrangement
allows the press sagging 402 to form the proximal inner
circumferential surfaces 431. This makes it possible to easily
produce the proximal inner circumferential surfaces 431 in the
packing 4.
[0091] As previously described, the first exemplary embodiment of
the present disclosure provides the spark plug 1 having an improved
structure, and the method of producing the spark plug 1 while
suppressing the insulator 3 from being broken during the production
of the spark plug 1.
Second Exemplary Embodiment
[0092] A description will be given of the spark plug and method of
producing the spark plug according to a second exemplary embodiment
of the present disclosure with reference to FIG. 11 and FIG. 12.
The second exemplary embodiment provides the spark plug 1 having
the packing 4 of the improved structure, and the method of
producing the spark plug having the packing 4.
[0093] FIG. 11 is an enlarged view of the surrounding part of the
packing 4 in the spark plug 1 produced by the method according to
the second exemplary embodiment of the present disclosure.
[0094] In the spark plug produced by the method according to the
second exemplary embodiment, distal inner circumferential surfaces
432 are formed adjacent to the inner periphery side of the housing
side contact surface 42, and distal outer circumferential surfaces
442 are formed adjacent to the outer periphery side of the housing
side contact surface 42. Each of the distal inner circumferential
surfaces 432 and the distal outer circumferential surfaces 442 has
a curved surface which is smoothly connected to the housing side
contact surface 42.
[0095] In the structure of the spark plug 1 according to the second
exemplary embodiment shown in FIG. 11, the distal inner
circumferential surface 432 is formed at the end part of the inner
periphery side surface 43, i.e. at the housing side contact surface
42 side of the packing 4. The distal inner circumferential surface
432 has a curved surface of a chamfer at the proximal end side of
the packing 4 in a diagonally inner circumferential direction.
[0096] Further, the distal outer circumferential surface 442 is
formed at the end part of the outer periphery side surface 44, i.e.
at the housing side contact surface 42 side of the packing 4. The
distal outer circumferential surface 442 has a curved surface of a
chamfer at the proximal end side of the packing 4 in a diagonally
outer circumferential direction.
[0097] On a cross section of the packing 4 in a direction running
on the central axis of the spark plug 1 and parallel to the plug
axial direction Z, each of the distal inner circumferential surface
432 and the distal outer circumferential surface 442 has a
curvature radius of not less than 5 .mu.m. In particular, no burr
line is formed in the packing 4 in the spark plug 1 according to
the second exemplary embodiment. On the other hand, the packing 1
according to the first exemplary embodiment has the burr line 45
shown in FIG. 4. The other components of the spark plug 1 according
to the second exemplary embodiment are the same as those of the
spark plug according to the first exemplary embodiment.
[0098] A description will now be given of the method of producing
the spark plug 1 according to the second exemplary embodiment with
reference to FIG. 12.
[0099] FIG. 12 is a view showing the method of producing the
packing according to the second exemplary embodiment. In
particular, FIG. 13 showing a schematic view a packing member 40
and the method of polishing the packing member 40 to form the
packing 4 in the spark plug 1.
[0100] Similar to the punching step described in the first
exemplary embodiment, the second exemplary embodiment performs the
punching step of producing the packing member 40 having a ring
shape. The press burrs 401 are formed in the packing member 40 (see
FIG. 7). As previously described, the method according to the
second exemplary embodiment produces the packing member 40, and
assembles the produced packing member 40 as the packing 4 with the
spark plug 1.
[0101] As shown in FIG. 12, before the assembling of the packing
member 40 with the spark plug 1, the method performs a barrel
polishing step of polishing the packing member 40 so as to form a
curved surface on the corners of the packing member 40.
[0102] In the barrel polishing step, packing members 40 having
press burrs 401 produced by the punching step are arranged in a
barrel 52 as a bowl shaped container. A fluid part 53 is arranged
in the barrel 52. The fluid part 53 is composed of water and
polishing materials.
[0103] The fluid part 53 is rotated in the barrel 53 so as to
contact the packing members 40 and the polishing materials in the
barrel 53. This step rounds the corners of the packing members 40,
and produces the packings 4 having a ring shape and rounded
corners.
[0104] The method arranges the packing 4 produced previously
described between the housing facing surface 21 of the housing 2
and the insulator 3. Similar to the method according to the first
exemplary embodiment, the method according to the second exemplary
embodiment produces the spark plug 1 with the packing 4.
[0105] The same reference numbers and characters between the second
exemplary embodiment and the first exemplary embodiment represent
the same components, and the explanation of the same components is
omitted here for brevity.
[0106] A description will be given of behavior and effects of the
spark plug and method according to the second exemplary
embodiment.
[0107] In the structure of the spark plug 1 according to the second
exemplary embodiment, each of the four corners of the packing 4 on
a cross section of the packing 4 in a direction parallel with the
plug central axis, i.e. each of the proximal inner circumferential
surfaces 431, the proximal outer circumferential surface 441, the
distal inner circumferential surface 432 and the distal outer
circumferential surface 442 has a curved surface which is smoothly
connected to the housing side contact surface 42.
[0108] In this structure of the spark plug 1, each of the distal
inner circumferential surface 432 and the distal outer
circumferential surface 442 has a curved surface, and is arranged
adjacent to the insulator side contact surface 41 in the packing 4
irrespective of the arrangement direction of the packing 4 viewed
from the plug axial direction Z.
[0109] This makes it possible to reduce the force applied from the
packing 4 to the insulator 3 without considering the arrangement
direction of the packing 4 to the housing 2. Accordingly, it is
possible for the method according to the second exemplary
embodiment to improve the productivity of the spark plug 1.
[0110] The method of producing the spark plug 1 according to the
second exemplary embodiment performs the barrel polishing step of
polishing the packing member 40. After the barrel polishing step,
each of the four corners of the packaging member 40, i.e. each of
the proximal inner circumferential surfaces 431, the proximal outer
circumferential surface 441, the distal inner circumferential
surface 432 and the distal outer circumferential surface 442 has a
curved surface. It is accordingly for the method according to the
second exemplary embodiment to easily produce the packing 4 having
the structure in which the overall corner parts, i.e. the proximal
inner circumferential surfaces 431, the proximal outer
circumferential surface 441, the distal inner circumferential
surface 432 and the distal outer circumferential surface 442 have a
curved surface. This increases the productivity of the spark plug
1. The spark plug and method according to the second exemplary
embodiment have the same behavior and effects of the spark plug and
method according to the first exemplary embodiment.
[0111] It is possible for the second exemplary embodiment to use
various known barrel polishing methods of polishing the packing
member 40. For example, as known barrel polishing methods, there
are a fluid type polishing method, a centrifugal force type
polishing method, a rotary type polishing method, a vibration type
polishing method, etc.
[0112] It is further possible for the second exemplary embodiment
to use a dry type barrel polishing method without using water,
instead of using a wet type barrel polishing method using the
barrel 53 filled with water.
[0113] A description will be given of experimental results and
evaluation results regarding the strength of the insulator in first
to fourth test sample groups G1 to G4 as spark plugs. Those test
sample groups G1 top G4 included various types of spark plugs which
have a different shape of the proximal inner circumferential
surfaces 431.
[0114] The experiment prepared the four test sample groups, i.e.
the first to fourth test sample groups G1 to G4 composed of spark
plugs having the proximal inner circumferential surfaces 431 of a
different shape. The spark plugs in the first to fourth test sample
groups G1 to G4 were produced by a different production method.
[0115] The packing 4 in each of the spark plugs belonging to the
first test sample group G1 was produced by the punching step
substantially equal to the punching step described in the first
exemplary embodiment. In the production of the spark plugs in the
first test sample group G1, the packing 4 was assembled with the
housing 2 while the press burrs in the packing were arranged facing
the insulator facing surface 31 of the insulator 3. In the first
test sample group G1 before the assembling step with the housing 2
after the punching step, each proximal inner circumferential
surface 431 of the packing 4 had the press burr which had a press
burr height of 5 .mu.m in the plug axial direction Z.
[0116] The packing 4 in each of the spark plugs belonging to the
second test sample group G2 was produced by the same punching step
and barrel polishing step as the punching step and barrel polishing
step performed by the second exemplary embodiment.
[0117] In the production of the spark plugs belonging to the second
test sample group G2, after the punching steps, the press burrs of
the packing were polished by the barrel polishing step so as to
have the corners of a curvature radius of 0 .mu.m. After the barrel
polishing step, the packing 4 was assembled with the housing 2
while the press burrs having the corners of the curvature radius of
0 .mu.m were arranged facing the proximal inner circumferential
surface 431 of the insulator 4. The packings in the spark plugs
belonging to the second test sample group G2 had the proximal inner
circumferential surface 431 which had the curvature radius of 0
.mu.m.
[0118] The packing 4 in each of the spark plugs belonging to the
third test sample group G3 was produced by the same production
method as the second exemplary embodiment. In particular, the
production method of producing the spark plugs in the third test
sample groups G3 performed the barrel polishing step during a time
period which was different from, i.e. longer than the time period
of the barrel polishing step of polishing the spark plugs belonging
to the second test sample group G2. The spark plugs belonging to
the third test sample groups G3 has the press burrs having a curved
surface having a curvature radius of 5 .mu.m.
[0119] After the barrel polishing step, the packing 4 was assembled
with the housing 2 while the press burrs having the curvature
radius of 5 .mu.m were arranged facing the proximal inner
circumferential surface 431 of the insulator 4. The packings 4 in
the spark plugs belonging to the third test sample group G3 had the
proximal inner circumferential surface 431 having the curvature
radius of 5 .mu.m.
[0120] The packing 4 in each of the spark plugs belonging to the
fourth test sample group G4 was produced by the same production
method as the second exemplary embodiment. In particular, the
production method of producing the spark plugs belonging to the
fourth test sample groups G4 performed the barrel polishing step
during a time period which was different from, i.e. longer than the
time period of the barrel polishing step of polishing the spark
plugs belonging to the third test sample group G3.
[0121] The spark plugs belonging to the third test sample groups G4
has the press burrs having a curved surface having a curvature
radius of 10 .mu.m.
[0122] After the barrel polishing step, the packing 4 was assembled
with the housing 2 while the press burrs having the curvature
radius of 10 .mu.m were arranged facing the proximal inner
circumferential surface 431 of the insulator 4. The packings 4 in
the spark plugs belonging to the third test sample group G4 had the
proximal inner circumferential surface 431 having the curvature
radius of 10 .mu.m.
[0123] The experiment prepared hundred test samples (spark plugs)
for each of the first to fourth test sample groups G1 to G4. That
is, the experiment performed the punching step so as to produce
each of the test samples as the spark plug having 0.4 mm thickness,
6.6 mm inner diameter and 7.6 mm outer diameter.
[0124] The experiment performed the test of each test sample on the
basis of ISO 11565 (ISO: International Organization for
Standardization). Specifically, each test sample as the spark plug
was fixed so that the plug axial direction Z of each test sample
was arranged to be aligned with a horizontal direction. The
experiment pressed a location 1 mm from the proximal end side of
the insulator measured from the distal end surface (i.e. from the
front end surface) of the insulator in the center of the plug
radial direction by 10 mm/min. Further, the experiment detected a
breaking load [N] at a time when being applying to the insulator
when the insulator was just broken. The experiment performed the
test at the room temperature.
[0125] Finally, the experiment disassembled each test sample and
performed a visible dye penetration test, i.e, a red check so as to
detect whether or not each test sample had been fractured.
[0126] The experiment detected whether a breakage weight of each
test sample is not less than 600 N or less than 600 N. When no test
sample belonging to each of the first to fourth test sample groups
G1 to G4 has the breakage weight of less than 600 N, the evaluation
result A is provided to this test sample group. On the other hand,
when at least one of 100 test samples belonging to each of the
first to fourth test sample groups G1 to G4 has the breakage weight
of less than 600 N, The evaluation result B is provided to this
test sample group.
[0127] Table 1 shows the experimental results of the test samples
belonging to each of the first to fourth test sample groups G1 to
G4. In Table 1, Press burr height [.mu.m] represents a height of
press burrs, in the plug axial direction Z, formed at the proximal
inner circumferential surface 431 in the packing 4 in each test
sample. Curvature radius [.mu.m] represents a curvature radius of
the proximal inner circumferential surface 431 in each test sample
belonging to the second to fourth test sample groups G2 to G4 after
the punching step. Also shown are the ratio of the number of test
samples having a breaking load of less 600 N in 100 test samples
belonging to each test sample group, and an evaluation result
representing an evaluation of a strength of the insulator in each
of the first to fourth test sample groups G1 to G4.
TABLE-US-00001 TABLE 1 Press Ratio of number of test burr Radius
samples having breaking load height Curvature of less 600N in 100
test samples Evaluation [.mu.m] [.mu.m] of each test sample group
results First test sample group G1 5 -- 40/100 B Second test sample
group G2 -- 0 2/100 B Third test sample group G3 -- 5 0/100 A
Fourth test sample group G4 -- 10 0/100 A
[0128] As can be understood from the evaluation results shown in
Table 1, when a test sample has press burrs (i.e. the test samples
belonging to the first test sample group G1), formed at the
proximal inner circumferential surface 431, having a press burr
height of 5 .mu.m in the plug axial direction Z before the
assembling step with the housing 2 after the punching step, 40 test
samples in the overall 100 test samples in the first test sample
group G1 have the breaking load of less than 600 N. It can be
understood that the formation of press burrs formed at the proximal
inner circumferential surface 431 often causes a breakage of the
insulator in the spark plug.
[0129] As can be understood from the evaluation results shown in
Table 1, when a test sample having the packing 4 in which the
proximal inner circumferential surface 431 has a curvature radius
of 0 .mu.m (i.e. has a sharp shape), two test samples in the
overall 100 test samples belonging to the second test sample group
G2 have the breaking load of less than 600 N. Accordingly, it can
be understood that there is a risk of breakage of the insulator in
a spark plug when the proximal inner circumferential surface 431 in
the packing 4 has a curvature radius of 0 .mu.m (i.e. has a sharp
shape).
[0130] On the other hand, as can be clearly understood from the
evaluation results shown in Table 1, when a test sample has the
packing 4 in which the proximal inner circumferential surface 431
has a curvature radius of not less than 5 .mu.m, the overall 100
test samples belonging to the third and fourth test sample groups
G3 and G4 have the breaking load of not less than 600 N.
Accordingly, it can be understood that it is possible to prevent
the insulator from being broken when the proximal inner
circumferential surface 431 in the packing 4 has a curvature radius
of not less than 5 .mu.m.
[0131] The experiment provides that it is difficult to produce the
proximal inner circumferential surface 431 having the curvature
radius of 20 .mu.m or more. It is preferable for the spark plug to
have the packing 4 in which the proximal inner circumferential
surface 431 has the curvature radius of not more than 20 .mu.m.
Third Exemplary Embodiment
[0132] A description will be given of the spark plug and method of
producing the spark plug according to a third exemplary embodiment
of the present disclosure with reference to FIG. 13 and FIG.
14.
[0133] The third exemplary embodiment provides the spark plug and
method of producing the packing 4 in the spark plug.
[0134] FIG. 13 is a view showing the method of producing the
packing in the spark plug according to the third exemplary
embodiment. In particular, FIG. 13 shows the packing member 40 and
a surface pressing jig 54 before pressing the packing member 40 by
using the surface pressing jig 54. FIG. 14 is a view showing the
method of producing the packing according to the third exemplary
embodiment. In particular, FIG. 14 shows the packing member 40 with
burr lines, designated by the reference number 45 shown in FIG. 4,
formed by pressing the press burrs 401 shown in FIG. 13 on the
surface of the packing member.
[0135] As shown in FIG. 13 and FIG. 14, the method according to the
third exemplary embodiment provides the spark plug 4 having the
packing 4 in which the burr lines 45 (see FIG. 4) are formed. On
the other hand, as previously described, the method according to
the second exemplary embodiment provides the spark plug 4 having
the packing 4 without any burr line. Other components of the spark
plug according to the third exemplary embodiment have the same
structure as the spark plug according to the second exemplary
embodiment.
[0136] Similar to the method according to the first and second
exemplary embodiments, the punching step punches the packing member
40 to have a ring shape. As shown in FIG. 13, the punching step
generates press burrs 401 in the packing member 40.
[0137] After the completion of the punching step, the method
according to the third exemplary embodiment performs a pressing
step which presses the surface of the press burrs 401, formed on
the packing member 40, by using the surface pressing jig 54. The
surface pressing step deforms the press burrs 401 formed on the
corners of the packing member 40, and forms a curved surface at
each corner of the packing member 40 so that each corner of the
packing member 40 has a curved surface. The method according to the
third exemplary embodiment performs the remaining steps which are
the same steps as the second exemplary embodiment.
[0138] As previously described, the surface pressing step presses
the press burrs 401 formed at the corners of the packing member 40.
This step forms the burr lines 45 (see FIG. 4) on the inner
circumferential edge parts and the outer circumferential edge part
at which the press burrs 401 have been formed.
[0139] In the production of the spark plug 1 according to the third
exemplary embodiment, the burr lines 45 are covered with plating by
a plating step after the surface pressing step. The burr lines 45
have been remained inside the plating. It is accordingly possible
to easily detect the presence of the bur lines 45 formed in the
packing 4 by observing a cross section of the packing 4 in the
spark plug 1.
[0140] Other behavior and effects of the spark plug and method
according to the third exemplary embodiment are the same as those
according to the second exemplary embodiment previously
described.
Fourth Exemplary Embodiment
[0141] A description will be given of the spark plug and method of
producing the spark plug according to a third exemplary embodiment
of the present disclosure with reference to FIG. 15 and FIG.
19.
[0142] The fourth exemplary embodiment provides the spark plug and
method of producing the spark plug 1.
[0143] A description will be given of the method of producing the
packing 4 according to the fourth exemplary embodiment.
[0144] FIG. 15 is a view showing a packing formation step composed
of a first formation step and a second formation step according to
the fourth exemplary embodiment. In particular, FIG. 15 shows the
plate member 400 arranged on a first forming die 55 before the
punching. The packing formation step uses the first forming die 55,
a second forming die 56 and a punching tool 57.
[0145] The first forming die 55 has a cylindrical shape. The
punching tool 57 is formed to be inserted inside the first forming
die 55. The second forming die 56 is arranged facing the first
forming die 55 in a formation direction D of the first forming die
55 shown in FIG. 15. The second forming die 56 also has a
cylindrical shape. The formation direction D of the first forming
die 55 coincides with the penetration direction of the inside
chamber of the first forming die 55.
[0146] The first forming die 55 has a first facing surface 551 of a
tapered shape. The second forming die 56 has a second facing
surface 561 of a tapered shape. Each of the first facing surface
551 of the first forming die 55 and the second facing surface 561
of the second forming die 56 is formed to be inclined in the inner
periphery side thereof at a first direction D1 side of the
formation direction D shown in FIG. 15.
[0147] The packing formation step has a first formation step and a
packing formation step.
[0148] As shown in FIG. 15, the first formation step arranges the
plate member 400 for the packing 4 at a second direction D2 side of
the first forming die 55 in a thickness direction of the plate
member 400 to coincide with the formation direction D of the first
forming die 55. FIG. 16 is a view showing the second formation step
of the packing formation step according to the fourth exemplary
embodiment. In particular, FIG. 16 shows a cross section of the
packing 4 in the second formation step after the first formation
step according to the fourth exemplary embodiment.
[0149] As shown in FIG. 16, the punching tool 57 punches the part
of the plate member 400, arranged on the first formation die 55, at
the inner periphery side and the outer periphery side of the first
forming die 55 in the first direction D1 side from the second
direction D2 side of the first forming die 55. The first formation
step produces the packing member 40 having a ring shape. The
produced packing member 40 is arranged between the first facing
surface 551 of the first forming die 55 and the second facing
surface 561 of the second forming die 56 which are arranged facing
from each other.
[0150] In the second formation step, the packing member 40 is
arranged between, i.e. pinched by the first facing surface 551 of
the first forming die 55 and the second facing surface 561 of the
second forming die 56, and the second forming die 56 pushes the
packing member 40 in the first forming die 55 side. The second
formation step thereby produces the packing 4 having a tapered
shape which is tapered inwardly in the first direction D1 of the
second facing surface 561 of the second forming die 56.
[0151] FIG. 17 is a view showing the packing 4 produced by the
packing formation step according to the fourth exemplary embodiment
of the present disclosure. As shown in FIG. 17, the packing
formation step produces the packing 4, and the packing 4 has the
press burrs 401 which are formed at the inner circumferential edge
part and the outer circumferential edge side and project in the
first direction D1 side of the formation direction D. Further,
packing 4 has the press sagging 402 at the inner circumferential
edge and the outer circumferential edge at the second direction D2
side.
[0152] A description will now be given of the assembling step of
assembling the packing 4 with the spark plug 1 with reference to
FIG. 18 and FIG. 19.
[0153] FIG. 18 is a view showing the method of assembling the
packing 4 with the housing 2 and the insulator 3 in the spark plug
1 according to the fourth exemplary embodiment. In particular, FIG.
18 shows a partially enlarged cross section of a structure in which
the packing 4 are arranged between the housing 2 and the insulator
3 in the spark plug 1 according to the first exemplary
embodiment.
[0154] As shown in FIG. 18, the packing 4 is arranged at the
housing facing surface 21 of the housing 2 so that the press burrs
401 of the packing 4 face the housing facing surface 21 side, and
the press sagging 402 of the packing 4 faces the opposite (i.e. the
proximal end side) of the housing facing surface 21 side.
[0155] FIG. 19 is a view showing the method of producing the spark
plug 1 according to the fourth exemplary embodiment. In particular,
FIG. 19 shows a partially enlarged cross section of the spark plug
1 in which the packing 4 is deformed between the housing 2 and the
insulator 3 by an assemble step according to the fourth exemplary
embodiment.
[0156] As shown in FIG. 19, the insulator 3 is inserted from the
proximal end side of the housing 2 into the housing 2. Similar to
the method according to the first exemplary embodiment previously
described, the method according to the fourth exemplary embodiment
performs the pressing step of pressing the insulator 3 to the
housing 2 side so as to deform the packing 4 between the housing 2
and the insulator 3. That is, this pressing step forms the
insulator side contact surface 41 of the packing 4 which is in
contact with the insulator facing surface 31 of the insulator 3.
Further, this pressing step presses the press sag 402, formed
adjacent to the inner periphery side of the insulator side contact
surface 41, so as to form the proximal inner circumferential
surface 431 having a curved shape. Further, this pressing step
presses the press sag 402, formed adjacent to the outer periphery
side of the insulator side contact surface 41, so as to form the
proximal outer circumferential surface 441 having a curved
shape.
[0157] The press burrs 401 formed at the distal end side of the
packing 4 is pressed and deformed by the housing facing surface 21
of the housing 2. This pressing step further forms the burr lines
45 (see FIG. 4, for example) along the overall inner
circumferential and outer circumferential of the housing side
contact surface 42 of the packing 4.
[0158] As previously described, the packing 4 is assembled with the
spark plug 1. The production of the spark plug 1 according to the
fourth exemplary embodiment is completed.
[0159] Next, a description will be given of behavior and effects of
the spark plug 1 and the method according to the fourth exemplary
embodiment.
[0160] In the first formation step of the production of the spark
plug 1 according to the fourth exemplary embodiment, the punching
tool 57 punches the part of the plate member 400, arranged on the
first formation die 55, at the inner periphery side of the first
forming die 55 in the first direction D1 side from the second
direction D2 side of the first forming die 55. The first formation
step produces the press burrs 401 projecting in the first direction
D1 side on the plate member 400.
[0161] In the second formation step after the first formation step,
the plate member 400 is arranged in the formation direction D
between the first forming die 55 and the second forming die 56
shown in FIG. 15. The first forming die 55 and the second forming
die 56 produces the packing 4 having a tapered shape which is
tapered in the inner periphery side along the first direction D1
shown in FIG. 16.
[0162] Accordingly, it is possible to recognize the projection
direction of the press burrs 401 on the basis of the tapered
direction of the tapered shape of the packing 4 after the first
formation step and the second formation step. Although the press
burrs 401 have a small size, it is possible to easily recognize
that the press burrs 401 are formed in the packing 4 after the
first formation step and the second formation step, i.e. to easily
recognize that the press burrs 401 are formed inwardly in the
reduced diameter side, i.e. to the first direction D1 side.
[0163] Accordingly, it is possible to prevent the press burrs 401
of the packing 4 from being arranged in the insulator facing
surface 31 side, i.e. possible to easily and correctly arrange the
packing 4 between the housing facing surface 21 of the housing 2
and the insulator facing surface 31 of the insulator 3.
[0164] In addition to the behavior and effects previously
described, the spark plug and method according to the fourth
exemplary embodiment have the same behavior and effects as those of
the first exemplary embodiment.
[0165] While specific embodiments of the present disclosure have
been described in detail, it will be appreciated by those skilled
in the art that various modifications and alternatives to those
details could be developed in light of the overall teachings of the
disclosure. Accordingly, the particular arrangements disclosed are
meant to be illustrative only and not limited to the scope of the
present disclosure which is to be given the full breadth of the
following claims and all equivalents thereof.
* * * * *